The present invention relates to a method for temporary protection of blank surfaces against corrosion and to a component with a surface protected against corrosion.
Corrosion is a known problem. There are various approaches in order to prevent or reduce corrosion. In that connection, for example, the flow of electrons can be interrupted in that the chemical composition of the materials concerned is changed or in that the material to be protected against corrosion is separated from the electrolyte (for example, salty water). There are also, for example, methods which are based on the use of a protection layer or a protection coating, on the use of a medium which prevents formation of rust, or on the use of a surface passivation. Such protection layers are typically based on painting, organic layers, ceramic and anorganic layers, plastic coatings, platings with non-rusting metal, etc. Other layers, such as, for example, zinc, aluminium-based metal and magnesium-based metal are distinguished by the fact that they have a tendency to corrode more quickly than the surface to be protected (these layers are therefore also termed sacrificial layers). Means which prevent rust formation typically change the surface chemistry and form a kind of intermediate layer. The surface passivation mentioned in the introduction thereagainst is carried out typically by the application or production of an oxide layer.
The mentioned methods are essentially suitable for permanent protection.
However, the need also exists to protect blank metal surfaces only temporarily. Thus, for example, there are semi-finished products or finished products which have a blank metallic surface which has to be protected after production and until final use. As an example there may be mentioned drive shafts, tooth flanks of gearwheels, rails and the like. In that case it is important for a protection means to be able to be applied quickly and simply and able to be removed again later. The approaches mentioned in the introduction are, however, only conditionally suitable when the point is temporary protection of a blank metal surface.
Two different methods have proved themselves in practice, although these methods have disadvantages.
A blank surface is usually protected by a corrosion protection means which is applied to or sprayed onto the surface. In machine and vehicle construction and in machine plants there is used for this purpose, for example, a product which is sold under the name “Tectyl” (registered trademark of Daubert Chemical Company, Inc., Chicago, Ill.). This product is distinguished by a good corrosion protection, but has the disadvantage that it can be removed only with difficulty. Particularly in the case of elevator construction, where guide rails are used for the elevator car or the counterweight and the running surfaces of such rails must be absolutely smooth and clean, such a protection means, which is removable only with cost in order to be again free of residue, is only conditionally suitable.
The use of solvents in order to expose the blank surface again also has disadvantages, since these solvents can be environmentally harmful and therefore expensive in handling.
The sacrificial layers mentioned in the introduction are also not suitable for a temporary protection, since they have the disadvantage that they enter into an intimate connection with the surface to be protected and cannot be removed again or can be removed only with a substantial outlay on processing. Moreover, they change the properties of the blank surface and thus cannot be used with guide rails, drive shafts and the like.